If you pay, do you get a Ts&Cs that don't contain any wording like this? Still, even if there was no specific "we own everything" statement there could be pretty much standard statement of "we'll retain data as required for the delivery and improvement of the service" which is essentially the same thing.
So, any company that allows it's employees to use chatgpt for work stuff (writing emails with company secrets etc) is definitely not engaging in "secure and private" use.
Unless there is very clear data ownership, for example, customer owns the data going in and going out. I can't see how it can be any different. The problem (not at all)OpenAI has in delivery such service is that in contrast to open source models I'm told there is a lot of "secret sauce" around the model(not just the model itself). Specifically input/output processing, result scoring and so on.